JPH0131019B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply method for a multi-cylinder internal combustion engine used in a vehicle such as an automobile, and more particularly to a fuel injection type fuel supply method for a two-intake multi-cylinder internal combustion engine.

Some two-intake multi-cylinder internal combustion engines are equipped with an intake port having a straight passage and a helical passage for each cylinder. Intake swirl occurs in the room.

Conventionally, in the above-mentioned two-intake multi-cylinder internal combustion engine, fuel is supplied to the helical passage, and in this case, fuel atomization is promoted, but the fuel is unevenly distributed around the outer periphery of the combustion chamber due to the intake swirl, and as a result, the air-fuel ratio of the mixture in the central region of the combustion chamber becomes larger than that in the outer periphery of the combustion chamber. A rich mixture exists and a relatively lean mixture exists in the central region of the combustion chamber,
Such a stratified state of the air-fuel mixture is unfavorable for the ignitability of the air-fuel mixture by the spark plug. That is, in a multi-cylinder internal combustion engine, the spark plug is generally located closer to the center area than the outer peripheral area of the combustion chamber, and therefore a relatively thin air-fuel mixture exists in the area where the spark plug is installed. If the average air-fuel ratio of the air-fuel mixture taken into the combustion chamber is a lean mixture close to the lean air-fuel ratio limit, the flammable air-fuel mixture within the lean air-fuel ratio limit will occur in the ignition plug installation area in the central region of the combustion chamber. There is a risk that ignition failure may occur. For this reason, conventionally, even if a good intake air swirl is obtained within the combustion chamber, the lean air-fuel ratio limit of the combustible mixture cannot be expanded effectively enough.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel supply method for supplying fuel to the above-mentioned two-intake multi-cylinder internal combustion engine so that the ignition of the air-fuel mixture by the ignition plug can be performed satisfactorily.

According to the present invention, each cylinder is provided with an intake port having a straight passage and a helical passage, and the straight passage directs the intake air more directly to the spark plug installation part in the combustion chamber than the helical passage. In the fuel supply method for a multi-cylinder internal combustion engine configured, fuel is injected only toward the straight passage, and fuel is supplied from the straight passage into the combustion chamber in the latter half of the intake stroke. This is accomplished by a method.

According to the fuel supply method according to the present invention as described above, fuel is supplied into the combustion chamber only from the straight passage in the latter half of the intake stroke, so that the average air-fuel ratio of the air-fuel mixture taken into the combustion chamber becomes a lean air-fuel ratio. Even if the air-fuel ratio is set close to the limit, a relatively rich flammable mixture with excellent ignitability will stably exist in the area where the spark plug is installed, expanding the average air-fuel ratio limit of the flammable mixture. Become so.

In particular, in the fuel supply method according to the present invention, since fuel is supplied to the combustion chamber in the latter half of the intake stroke, the fuel supplied into the combustion chamber is disposed of by the spark plug by the intake swirl during the intake stroke. There is no undesirable diffusion of fuel into areas further away from the spark plug installation area, and this prevents undesirable diffusion of the fuel mixture into the area of the spark plug installation area, in addition to the fact that the fuel supply to the combustion chamber is through a straight passage. An air-fuel mixture with an appropriate air-fuel ratio for ignition is more stably and reliably present, and the operability of the internal combustion engine with a lean air-fuel mixture, that is, lean burn performance, is further improved.

The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing one embodiment of a multi-cylinder internal combustion engine equipped with a fuel supply device that implements the fuel supply method according to the present invention. In the figure, numeral 1 indicates a multi-cylinder internal combustion engine, and the multi-cylinder internal combustion engine has a cylinder block 2 and a cylinder head 3. The cylinder block 2 receives a piston 4 in a plurality of cylinder bores (cylinders) (only one of which is shown in the figure) formed therein, and above the piston 4, the cylinder It works together with the head to define the combustion chamber 5.

The cylinder head 3 has one inlet end 6 for each cylinder and two outlet ends 7 and 8 opening into the combustion chamber 5.
An intake port 9 and an exhaust port 30 are formed. As clearly shown in FIG. 2, the open end 7 of the intake port 9 is relatively small, and the open end 7 and the inlet end 6 are connected by a straight passage 10, whereas the open end 8 is relatively large. , the opening end 8 and the inlet end 6 form a helical passage 1
1. The open end 7 is opened and closed by a first intake valve 12, and the open end 8 is opened and closed by a second intake valve 13. The exhaust port 30 is opened and closed by an exhaust valve 31.

Further, an ignition plug 24 is attached to the cylinder head 3, and the spark discharge portion of this ignition plug installation portion 24 is located in the central region of the combustion chamber 5.

The straight passage 10, which communicates with the combustion chamber 5 through the open end 7, has a smaller diameter than the helical passage 9, which communicates with the combustion chamber 5 through the open end 8, as shown in FIG. It is located on the center side when viewed in the radial direction, and directs intake air directly to the spark discharge portion of the spark plug 24.

The intake port 9 is connected at its inlet end 6 to an intake manifold 14 . Intake manifold 1
4 is integrally formed with a surge tank 15, and air is supplied to the surge tank 15 through a throttle body 20 that includes an air cleaner 16, an air flow meter 17, and a throttle valve 19. Further, the upstream side of the throttle valve 19 of the throttle body 20 and the surge tank 15 are connected by a bypass passage 22 having an air valve 21 in the middle.

The multi-cylinder internal combustion engine 1 has a fuel injection valve 23 for each cylinder.
As clearly shown in FIG. 2, this fuel injection valve 23 is designed to inject liquid fuel such as gasoline from a straight passage 10 of the intake port 9 toward the open end 7. There is.

FIG. 3 shows a fuel injection control device that controls the valve opening time (fuel injection amount) and valve opening timing (fuel injection timing) of the fuel injection valve 23. In FIG. 3, 23 ₁ to 23 ₄ indicate the fuel injection valves of each cylinder, and the suffix numbers correspond to the cylinder numbers. The fuel injection control device includes a microcomputer 25.
5 calculates the intake air amount per stroke based on the intake chamber air amount detected by the air flow meter 17 and the engine rotation speed detected by the rotation speed sensor 26, determines the fuel injection amount accordingly, and Based on the cylinder discrimination signal from the reference signal oscillator 27 and the crank angle detected by the crank angle sensor 28, it is determined which cylinder is in the intake stroke, and a fuel injection signal (valve opening signal) is generated based on the determination result. It is designed to sequentially output to each of the drive circuits 29 ₁ to 29 ₄ of each fuel injection valve. Microcomputer 2
5 outputs the fuel injection signal to each of the drive circuits 29 ₁ to 29 ₄ when the cylinder into which fuel is injected from the fuel injection valve corresponding to the drive circuit is in the latter half of the intake stroke.

By outputting the fuel injection signal as described above, each of the fuel injection valves 23 ₁ to 23 ₄ enters the straight passage 10 when the corresponding cylinder is in the latter half of the intake stroke, as shown in FIG. Open end 7
Inject liquid fuel towards. At this time, since the intake valve 12 is open, the liquid injected from the fuel injection valve does not stay in the intake port 6 but immediately flows into the combustion chamber 5 and enters the central area within the combustion chamber 5. It becomes more and more unevenly distributed. As a result, a relatively rich air-fuel mixture exists in the central region of the combustion chamber 5, and a thin air-fuel mixture gradually exists in a layered manner toward the outer circumference. The rich air-fuel mixture in the central region is ignited, and combustion starts from this rich air-fuel mixture, resulting in stratified combustion.

Although specific embodiments of the present invention have been described in detail above, those skilled in the art will recognize that the present invention is not limited thereto and that various embodiments can be made within the scope of the present invention. It should be obvious.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a multi-cylinder internal combustion engine implementing the fuel supply method according to the present invention, and FIG. 2 is a schematic diagram showing one embodiment of the multi-cylinder internal combustion engine shown in FIG. FIG. 3 is a plan view showing the positional relationship of the intake and exhaust ports, FIG. 3 is a block diagram showing one embodiment of the fuel injection control device used to carry out the fuel supply method according to the present invention, and FIG. 4 shows the stroke of each cylinder. It is a graph which shows the fuel injection timing. DESCRIPTION OF SYMBOLS 1...Multi-cylinder internal combustion engine, 2...Cylinder block, 3...Cylinder head, 4...Piston, 5
... Combustion chamber, 6 ... Inlet end, 7, 8 ... Outlet end,
9...Intake port, 10...Straight passage, 1
1... Helical passage, 12, 13... Intake valve, 1
4... Intake manifold, 15... Surge tank, 16... Air cleaner, 17... Air flow meter, 18... Intake tube, 19... Throttle valve, 20... Throttle body, 21... Air valve, 22... Bypass passage , 23... Fuel injection valve, 24... Spark plug, 25... Microcomputer, 26... Rotation speed sensor, 27... Reference signal transmitter, 28... Crank angle sensor, 29
₁ ~ 29 ₄ ... Drive circuit, 30 ... Exhaust port, 3
1...Exhaust valve.

Claims (1)

[Claims] 1. A fuel for a multi-cylinder internal combustion engine, in which each cylinder is provided with an intake port having a straight passage and a helical passage, and the straight passage is configured such that the intake air is directed more directly to the spark plug installation part in the combustion chamber than the helical passage. A fuel supply method characterized in that fuel is injected only toward the straight passage, and fuel is supplied from the straight passage into a combustion chamber in the latter half of an intake stroke.